Projection apparatus



Patented Aug. 31; 1937 2,091,705 PROJECTION arrana'rus Puno T.Farnsworth. san Francisca, cauf., assignor to Farnsworth TelevisionIncorporated.. a corporation o! California application November s, 1934,serial No. '151,116

150mm (ctms-.sr

My invention-relates to apparatus for the projection of motion pictures,and particularly to such apparatus adapted to be used in conjunctionwitha television transmitter.

Among the objects 'of my invention are: to provide, in motion pictureprojection, apparatus for use in conjunction with a televisiontransmitter wherein successive picture frames ot the nlm areintermittently moved through a beam of light and positioned beforescanning means, a shutter which permits-a longer interval-of exposure ofpicture areas between periods when the light be'am is cut off to permitshiftingof the lm; to provide a shutter which, when operated with aprojector having a moderate speed lm shifting mechanism, produces theeiect of a high speed mechanism, by shortening the cut-oli periodbetween successive exposures of the film; to provide a shutter for usein apparatus for the transmission of television motion pictures whichpermits, during each scansion, an increase in the number of pictureelements and consequently produces an image' having ner detail; toprovide a shutter for the use above described, which, in a cathode rayimage dissector tube, by lengthening the interval of exposure of eachpicture frame, permits slower movement of the scanning beam over thearea to be scanned and consequently the signal output from such a tubeis materially increased due to the additional energy collected duringeach scansion; to provide, in apparatus of the character described,projection means for a motion picture film, which, while operable toproject a series of images considerably in excess of the frequencynecessary to maintain persistency of vision, will produce intervals ofexposure of eachv image equivalent to that obtainable with* such afrequency without introducing the objectionable icker identifiedtherewith; to provide the combination, in television apparatus havingmeans for scanning, insucceesive elemental areas, an illuminated opticalimage projected from a motion picture lm, of means for permitting fullexposure of that elemental area of the image being scanned, forgradually increasing to full exposure those exemental areas of the imageto be` a beam of light projected vfrom a source to a screen throughmeans for defining the cross sectional shape of the beam, vso thatportions of the dened area of the beam projected on the screen willremain stationary when the beam-defining 5 means is moved transverse to'the axis of the beam; to provide an improved shutter which may readilybe incorporated in existing projectors for television use; and toprovide improved apparatus for the transmission of televised motionpictures. 10v

Other objects of my invention will be apparent or willbe specificallypointed out in the description forming a part of this specification, butI do n'ot limit myself to the'embodiment of the invention hereindescribed, as various forms may l5 be adopted within the scope of theclaims.

Referring to the drawing:

Figure 1 is an elevational view, mostly diagrammatic in character andreduced to lowest temas, o! a television transmission systemincorporating the 9 improved projection apparatus of my invention.

Figures 2 to 5 inclusive are diagrammatic views illustrating the meansfor refracting the projected light beam in different stages ofarrangement. 25

`Stated broadly, my invention comprises the combination, with apparatusfor projecting in lrapid sequence, a series of superposed opticalLimages on a surface from a motion picture lm, or other means for deningthe image, including means for intermittently moving elemental portionsof said lm or image-dening means into registry with a beam of lightemanating from a light source and projected on said surface, andallowing said elemental portions to dwell for in- 35 tervals inj saidbeam, and a shutter for intersecting said beam at other intervals tovobstruct passage of portions of thebeam to the surface during movementof the 51m; of means operating in conjunction with said shutter forrefracting portions of the beam so that portions of the a reailluminated by the-beam on the surface will remain in stationaryrelationship thereto during a A portion oi' .the movement of the film orbeamdening vmeans.

At the present time extensive research work is being carried on in theeld of the transmission of motion pictures by television. Heretofore, ithas been the practce toutilize a standard mo- 5 tion picture projectorfor reproducing a series of optical images from the motion picture lm.which images may te scanned, in succession, by any of the several tntthods of scanning well known in the television art, to produce a trainci television signals. n

PATENT o1-Fics -l I into registry with the light beam. It will be seen,

therefore that in televising a single image, a complete scansion thereofmust occur within that 15 fraction of a second comprising the stationaryperiod. 'I'his means that, in order to produce a television imagepossessing the number of picture elements of a size necessary to bringout the fine detail of the image, the length of time that each 20element of the image is exposed to the scanning means is exceedinglyshort, due to the speed at which the scanning means must travel in orderto cover the exposed image inA the allotted time. The overall time of acomplete lm cycle cannot 25 be changed, due to the sound requirement ofa ninety feet per minute rate of progression.

I have found that, without material alteration, the standard motionpicture projector can be made to increase the time available Aforscansion without changing the existing ratio between the intervals ofmovement and rest of the film, and that the time between scansions maybe decreased accordingly. This is accomplished by providing a shutter,including a prism of material permeable to light. in one dimension androtatable in synchronism with the movement of the film. This prismoperates during the portions of time when the lm is moving to refractthe light beam and displace a portion of the 40 projected image withrespect to the picture on the film so that it is in position to bescanned before the film comes to rest in the light beam.'

and similarly to maintain a portion of the image in position when thefilm again starts to move.

5 This means that scansion of the image may start before the film comesto rest and may continue after the lm has started to move to bring thenext succeeding picture frame into registry with the light beam.

In greater detail, the apparatus shown in Figure 1 represents apparatus,including one preferred form of the shutter of my invention, which maybe used to transmit motion pictures by television. 'The film 2,depicting the action to be 55 transmitted, is moved, by the intermittentsprocket 3, in .the usual successive increments past the aperture 4,formed in a plate 5, which denes the light beam 6 emanating from thesource 'I and passing through the condensing 60 lens 8. An objectivelens system 9 is provided in the path of the light beam for focusing thebeam before suitable scanning apparatus.

A While any of the several known types of electrical or mechanicalscanning devices ma; be

55 used in the practice of my invention, v1- prefer to use a devicesimilar to the image dissector tube shown and described in theapplication of Robert E. Rutherford', entitled Image dissector andmethod of electron beam analysis, Serial No.

70 696,999, led November 7, 1933; or I may prefer to use a variant tubeshown and described in United States Patent No. 1,773,980, entitledTelevision system, issued to me on August 26, 1930.

Broadly; the latter tube comprises an evacu- 75 ated envelope having atransparent end portion.

image.

A photosensitive cathode is disposed at one end of the envelope, and a,metallic screen anode. structure including a sleeve having an`aperturetherein, behind which is positioned a target electrode, is located atthe other end of the tube 6 opposite the cathode. An optica! imagefocused on the photosensitive cathode will institute an electron iiowtherefrom having elemental cross sectional densities corresponding tothe light ln- .tcnsities of elemental portions of the optical '0 Byproviding the anode structure lwith a charge positive with respect tothe cathode,

a uniform electrostatic 'field is established between the electrodeswhich causes the electrons emanating from the cathode surfacentobemainl5 I tained in their original relationships and to be accelerated ina defined beam in the direction of the anode. This beam is now actedupon by the magnetic fields of deiiecting coils, energized n byoscillators adjusted to suitable frequencies, which cause the beam to bedeected cyclically in two directions before the anode aperture.Successive elemental portions of the electrons in the beam will beadmitted to the target electrode, and since the density of the electronsof the entering portion of the beam-is proportional to the degree oflight intensity o! that' portion Aof the optical image, at the cathode,from which the electrons originated, these successively collectedelectrons may be passed through an 3 amplifier and thence to a radio orline system for transmission as a train of television signals. TheRutherford tube is shown diagrammatically in Figure 1, and differs fromthe tube just described only in operation and in that the screen elementof the anode structure has been dispensed with. Substantially the sameenvelope IIis used 4having a transparent window I2 in the end thereofand a photosensitive cathode I3 positioned at the other end thereof. The40 anode structure comprising the tubular linger I4, provided with anaperture I6, projects into the tube from the side wall thereof with theaperture I6 facing the cathode. A target eiec- 'trode I I is positionedwithin the nger I4 and 45 behind the aperture.

Since the electrostatic field between anode and cathode is asymmetrical,the electrons leaving the surface of the cathode I3 will not, `as wasthe case in my tube described previously, be accelerated toward theanode in a beam having elemental cross sectional densities correspondingto the light intensities of the areas of the cathode from vwhich theyoriginated, but will tend to follow random paths. However, by theaddition of magnetic focusing means, not shown, but comprising asolenoid coil disposed about the axis of the tube, and energized from asource of direct current, a constant intensity magnetic field isestablished parallel with the axis o f the tube ysothat the electronsare causedv to follow substantially helical paths and'may be made, bycorrect adjustment of the various elds, to arrive, in the area of theanode aperture, in the same numerical relationship in which theyleft-,the cathode. It will be understood, however, that by deflectingthis beam cyclically before the aperture, by means of deeo-TE? tioncoils I8 and I9, driven by suitable oscil- 70 lators 2i and 22respectively, to permit collec- A tion by the target electrode, ofelemental portions thereof, a train of television signals will beproduced which may be conducted by the lead t0 amDHfVnQ anmrnhic 91 ff-6 "g i5 GXDOSed picture frame.

interval of time in which the electrons from a given eiemental area ofthe cathode are allowed tc pass through the anode aperture. Since, due lto the necessity of'maintaining the rate oi nlm v movement at twentyfour picture frames per second, the time per scansion usually beinglimited to one forty-eighth of a second, it will Abe seen that, due tothe speed at which the l beam sweeps past the aperture, only a smallt-ime factor lsavailable for the collection oi'elec.--

1 trons from any vone elemental area. As a result of this the amplitudeof the signal output of the tube is relatively low. To increase thesignal strength the natural tendency would be to decrease the frequencyof deflection so as to permit a greater electron admittance to thetarget electrode. 'Ihis means a considerable` reduction in the number ofpicture elements and conseq uently a loss in detail of the reproducedimage'.

I have found that it is possible, while maintaining the standard rate ofnlm movement, to lncrease the scansion time of each frame andcorrespondingly reduce the period of darkness between scansions thereof,this being due, in part, to a modification of the wave form of the lowfrequency oscillator, these two factors eiecting a considerable gain insignal output strength and in the number of picture elements obtainableduring each scansion.

This is accomplished by providing a gear 21 which is fixed on the shaftcarrying the intermittent sprocket 3. which 'gear is in mesh, through anidler gear 28, uith a pinion 29. The pinion is rotatable on a shaft 3|,whose longitudinal axis lies in a plane transverse to the central axisof the light 'beam C, and is connected for rotation with a tubularshutter frame 32, rectangular in cross section. A prism 33 of lightpervious material, preferably glass, is cemented or otherwise secured inthe shutter-frame. The gear ratio between the intermittent sprocketshaft and the shaft 3| is such that the shutter frame will make one halfrevolution for each quarter revolution of the sprocket; in other words,the shutter will make one half revolution during the shifting of eachsuccessive picture frame of the iilm 2.

Referring now to the diagrams shown in Figures 2 to 5 inclusive, we ndthat, in Figure 2, the positions of the elements are the same as inFigure l, which position they occupy during each exposure of the nlm.The film inthese diagrams is indicated by a. series of joined arrows,the distance between the points thereof representing the length of eachpicture frame. The light beam '6 has-been shown as comprising fourparallel zones which will be useful in describing the operation of theshutter and prism to be explained directly. The objective lens systemil,` of Figure G5 l, has been replaced, in the diagrams, with anapertured plate 34, similar to the plate 5, so that ,the deflection ofthe light beam may be more readily understood.

In Figure 3 the lm has started to move downwardly, to bring a newpicture frame into position before the aperture 5, and the shutter hasrotated so that the leading edge of the upper portion of the framethereof .has advanced into registry with the receding edge of thepreviously As the prism rotated,

from the position shown in Figure 2 to that shown in Figure 3, the.angle 'of the prism faces. with respect to the axis o! the beam.progressively changed with the result that the beam was reiracted inpassing through the prism an amount g corresponding to the distance thatthe picture frame had been displaced with respect to the aperture l.This progressively increasing refraction of the beam maintained theoptical image in the same relationship with the vaperture in the 1|plate 34 as existed when the film frame was po-v sitloned directlybefore the aperture 4. Further movement of the film and consequentlyrotation of the shutterlframe will cause the light beam tobe cut oil, asshown in Figure 4; and continued la movement'of the elements will createa condition which is shown in Figure 5; this being the reverse of whatoccurred during movement of the I shutter frame to the position shown inFimue 3,

in that the leading edge of the nextsucceeding 20 picture frame of thefilm has been refracted so that that portion of the picture exposedthrough the prism is already alined with the aperture in the plate 34even though the picture frame has not yet moved into alinement with theaperture 25 4. It will be readily seen by examination oi' the diagramsthat exactly a iifty percent increase in the exposure time of eachpicture frame is obtained between the cut oir of the image, asshown inFigure 3, and the start of exposure of the 30 image, as shown in Figure5. It will" alsobe seen that a. reduction of like percentage is'obtainedin the dark period between exposures of successive picture frames of thenlm.

While it is admitted that the shutter of my 35 -invention would notfunction eflicientlyA in the projection of motlcn pictures for visualentertainl ment purposes, due to the nonuniformity of exposure ofdifferent areas of the image occasioned by the spaced relationship,within the connes of 40 the projected image, of the points of inceptionand cut oir oi' the light beam, I am not concerned with this phase ofoperation, the object to be attained being the extension of the scansiontime ofeach picture frame to the maximum 45 obtainable during theinterval of time that the frame is moved into and out of registry withthe light beam. Thus, as long as complete exposure of the area' coveredby the optical image starts at one edge thereof, and progresses towardthe 50v other edge thereof in advance of the elemental area underscansion, there is no need of further continuing exposure of the partsof the image already scanned. As a result of this it will be 'v seenthat the fadeout of the image may follow 55 directly-in the wake oi' theelemental area being scanned, the final result being that, since thescanningmeans traversed only those areas of the image under fullexposure,`the resulting train o1' television signals is capable ofreproducing a 60 complete image having a uniform degree of brilliance.

The desirability of increased scansion time in the operation oftelevision transmitting tubes has beeny stated above, and I utilize thegain in scan- '65 sion time to provide for greaterv amplitude of theoutput oi' these tubes due to the extended time of exposure of the iilm,obtained with the shutter of my invention, to produce televised motionpictures of lincreased brilliance and fineness of de- 70' tail. It canbe easily understood that by modifying the saw-tooth wave form of theoscillator 2| to provide for a longer interval of time during theworking half cycle, and a corresponding shortening of the return halfcycle, a material increase 'u will be obtained in the time availableforthe scansion ofthe complete image. Consequently lt is possible totransmit a televised picture containing a greatly increased number ofpicture ele- 5 ments per scansion, or the same number of pictureelements w th greatly v increased signal strength.

'I'he shutter of my invention lends itself .well

to the system of interlaced scanning. This system is rapidly findingfavor'with the television research worker, and consists, broadly, in thesystems using cathode ray tubes, of adding a seconl dary pulse to thelow frequency defiecting coils so that, for example, where it isdesiredto scan l5 an object with a certain number of lines, only every otherline is traversed during one cycle, or

` deiiection. of the scanning beam, the secondary pulse causing adefiection of the scanned area during the second cycle, to' cause thescansion of Vlines which were not scanned during the first cycle.Although the complete image is scanned but once, the beam has coveredthe image field. twice. It will be seen that since the interval of 'timein which the image is maintained in a stationary position, when usingthe shutter above described, is materially extended over that whichobtained heretofore, ample time is afforded, by the use of the apparatusof my invention, in which the image may b e scanned a greater number oftimes than was possible with other mechanisms. Superiorresults and finerdetail in the reproduced image have been obtained by the use of thissystem. It will be understood that the image ma'y be scanned any numberof times, this being governed by the secondary pulse, the reference todouble scansion above being exemplary.

'I'he improved shutter just described is characterized by simplicity,ease of construction, ready applicability to existing motion picturepro- 40 jectors for the uses described above, and marks a distinctadvancement in the television art.v

I claim:

1. 'I 'he combination, with apparatus for the transmission of televisedmotion pictures of a focused light source, means for guiding a motion'picture film before said light source in registry with said televisiontransmission apparatus, driving means positioned to draw said filmintermittently past said light source, and arranged to maintain eachfilm frame stationary in registry with said light source and saidtelevision transmission apparatus, for a definite period of time, and todraw successive film frames into such registry during equal periods oftime, and means for maintaining the visual image exposed to the scanningmeans in a stationary position during move,- ment of the film.

2. The combination, with apparatus for the4 transmission 0 1'v televisedmotion -pictures of a focused light source, means for guiding a. motionpicture film before said light source in registry with said'televisiontransmission apparatus, intermittent-driving means positioned andarrangedl to draw said film past said light source, to maintainsuccessive frames of said film in registry with said light source forfixed periods of time and to utilize equal periods of time to shiftsuccessive lm frames into registry with said light source, and opticalmeans for refracting said beam dur- '70 ing movement of the film tomaintain said image in stationary relationship with said scanning means.

3. The combination, with apparatus for the transmission of televisedmotion pictures having a scanning device, a light source, a film guidepositioned opposite said source, driving means sc sitioned and arrangedas to draw film to be vised over said guide into registry with said Isource and said scanning device, and to main each frame of said lm insuch registry f certain period of time, and 4to displace said during anequal interval of time to bring the i successive frame intosuch'rcgistry, of means 'maintaining thevisual image projected onscanning means in a. stationary position duri: portion of the lmovementof the film, and mf for cutting ofI the beam of light during anoiportion o! the movement of the film.V 4. The combination, with apparatusfor transmission of televised motion pictures hai a scanning device, ofa light beam source. ai guide positioned opposite said source and in reitry with said light beam, intermittent-dmv means so positioned andarranged as to draw s cessive frames of the film to be televised over sguide into registry with said light beam and s scanning means, tomaintain each frame in si registry for a denite period of time, and tom1 successive frames into such registry during int mediate equal periodsof time, of means for p1 jecting a portion ofthe visual image of eachsaid frames into a stationary position on Sz scanning means prior to andbeyond the inten of time when the lm dwells in the light beam.

54. The combination, with apparatus for t transmission of televisedmotion pictures havi scanning means, a light beam source and an i;terposed film guide aligned with said light bca source, intermittentdriving means so positinl and arranged as to draw motion picture lm to itelevised over said guide into registry' with sa light beam and saidscanning means, to hold ea( frame of said filmln such registry for a.defini interval of time, and to displace said film durir an equalinterval of time to draw the next succeil ing frame of said lm into saidregistry, of optic: means interposed between said film and said scarning means for refracting said beam an amour related to the degree ofmovement of the film s that the projected image is maintained in stationary relationship with the scanning means dur ing movement of the lm.1

6. The combination, with apparatus for th transmission of televisedmotion pictures havin] scanning means, a light beam source and an interposed film guide aligned with said light bean source, intermittent.driving means so positionec and arranged as to draw motion picture filmt: be televised vover said guide into registry with saic light beam andsaid scanning means, to hold each frame of said film in such registryfor a definite interval of time, and to `displace said film during anequal interval of time to draw the next succeeding frame of said filminto said registry, of a shutter comprising a. rectangular prism oflight permeable material rotatably mounted in the path of vsaid beam andsynchronized with the movement of the film, for effecting, duringmovement of the film, a gradual displacement between the image on the lmand the projected image before the scanning means. Y

7. The combination, with apparatus for the transmission of televisedmotion pictures having scanning means, a light beam source and aninterposed film guide aligned with said light beam source, intermittentdriving means so positioned and arranged as to draw motion picture filmto be' televised over said guide into registf'ry with said light beamand said scanning means, to hmd each frame of said mm in' smh-...MMM Ainterval of time. and to dispiace said nlm during an equal interval oftime to draw the next succeeding frame oi said nlm into saidregistry,'oi` a shutter comprising a tubular rectangular frame mountedfor rotation in a plane transverse to the longitudinal axis oi the beam,and optical means mounted on said frame for 'refracting said beam duringme' vement of the film for maintaining the position ci.' the projectedimage in a stationary 1o position before the scanning means duringmovement of the iilm. A

8. The combination, with apparatus for the transmission of televisedmotion pictures having scanning means, a iight beamsource and an inl5terposed dim guide aligned with said light beam source, intermittentdriving means so positioned and arranged as to draw motion picture nlmto be televised over said guide'into registry with said light beam andsaid scanning means, to hold each 2o frame of said lm in such registryfor a definite interval o! time, and to displace said lxn during .anequal interval of time to draw the next succeeding frame of said iilminto said registry, of a shutter comprising a tubular rectangular framemounted for lrotation in a plane transverse to the longitudinal axis ofthe beam, and sychronized with the movement of the iilm,and a prism oflight permeable material mounted on said frame for refracting said beamduring movement of the film for maintaining the position of theprojectedimage in a stationary position before the scanning means during movementof the film.

9. 'I'he combination, with apparatus for the transmission of televisedmotion pictures having scanning means, a light beam source and aninterposed lm guide aligned with said light beam source, intermittentdriving means so positioned and arranged as to draw motion picture lm tobe televised over said guide into registry with said 40 light beam andsaid scanning means, to hold each frame of said iilm in such registryfor a denite interval of time, and to displace said lm during an equalinterval of time to draw the next succeeding frame of said lm into saidregistry, of a shutter comprising a tubular rectangular frame mountedfor rotation in a plane transverse to the longitudinal axis of the beam,and rotatable at a peripheral speed in excess of the speed of move.-ment of the film, and a rectangular prism of light permeable materialhaving the sides thereof parallel to the axis of rotation thereofmounted on said frame for refracting said beam during movement of theiilm for maintaining the position of the projected image in a stationaryposition before the scanning means during movement of the 10. Thecombination, with an image dissector tube for use in a televisiontransmitter having a photosensitive cathode capable of emitting anelectron discharge having elemental cross sectional densitiescorresponding to the light intensities of elemental areas of an opticalimage projected thereon, means for accelerating said discharge in anelectrostatic eld to produce a i beam of cathode rays, and means fordeiiecting said beam cyclically in two directions past an electroncollecting electrode so that successive elemental portions of the beamwill be collected by the electrode to produce a train of television 70signals, of means for projecting an optical image on said cathode fromimages xed on a motion picture ilm, said means comprising a light beamsource directed toward said cathode, a film guide interposed betweensaid cathode and said light source, intermittent driving means sopositioned 'successive frame of said film into such registry cathodefrom images contained ona motion picture and arrangedastodrawsaidiilmtobetelevised over said guide, to'hold each film tramein such'registry with said vlight beam that the proiected image of saidframe will fall upon said cathode for a definite intel-val or time, todraw s the 'next successive frame .o i said film into such registryduring an equal intervall oi time, and optical means for maintaining theprojected image ci' each frame in a stationary position on said cathodeduring movement oi' said film'.

l1. The' combination, with an image dissector tube for use in atelevision transmitter having s photosensitive cathode capable ofemitting an electron discharge having elemental cross sectionaldensities corresponding to the light intensities of elemental areas ofanpptical image projected thereon, means for accelerating said dischargein an electrostatic eld to produce a beam 'i Y' of cathode rays,` andmeans for deecting said1 beam cyciically in two directions past anelectron 20 n collecting electrode so that successive elemental portionsof the beam will be collected by the f electrode to produce a train oftelevision signals, of means-for' projecting an optical image on saidcathode from images contained on a motion picture film, said meanscomprising a light beam source directed toward said cathode, a lm guideinterposed between said cathode and said light source, intermittentdriving means s o positioned and arranged as to draw said iilm to betelevised over said guide, to hold each iilm frame in such Aregistrywith said light beam that the projected image of said frame will fallupon said cathode for a denite interval of time, to draw the next 35during an equal interval of time, and optical 1' means for maintainingthe projected image of each frame in a. stationary vposition on saidcathode during movement of said lm.

l2. The combination, with an image dissector tube for use in atelevision transmitter having a photosensitive cathode capable ofemitting an electron discharge having elemental crosssectional densitiescorresponding to the light intensities of elemental areas of an opticalimage projected thereon, means for accelerating said discharge in anelectrostatic field to produce a beam of cathode rays, and means fordeiiecting said beam cyclically in two directions past an electron-collecting electrode so that successive elemental portions of the beam.will be collected by the electrode to produce a train of televisionsignals, of means for projecting an optical image on said lm which ismovable in successive increments g5 through a beam of light projected onsaid cathode, said means comprising a light beam source directed towardsaid cathode, a lm guide i y each frame in a stationary position vonsaid cathode during movement of said lm, said means comprising a prismof light-pervious material rotatably mounted in the path of said lightbeam, so positioned and arranged as to maintain said projected image ina stationary position on said cathode.

13. The combination, with an image dissector tube for use in a.television transmitterv having a photosensitive cathode capable ofemitting an electron discharge having elemental cross sec- -5 tionaldensities corresponding to the light intensities-oi elemental areas ofan optical image projected thereon, means for accelerating saiddischarge in an 'electrostatic iield to provide abeam of cathode rays,and means for deectingl said beam cyclically in two directions past anelectron collecting electrode so that successive f elemental portions ofthe beam will be 'collected by the electrode to produce a train oftelevision signals, of means for projecting an optical image l on saidcathode from images containedv on a motion picture ilm, said meanscomprising a light beam source directed toward ...said cathode, a nlmguide interposed between saidv cathode and said light source,intermittent driving means so positioned and arranged as to draw saidIilm tobe televised over said guide, to hold each film frame in suchregistry with said light beam that the projected image of said framewill fall upon said cathode for a denite interval of time, to

draw the next successive frame of said lm into such registry during anequal interval of time, and means for maintaining the projected image ofeach frame in a stationary position on said cathode during movementofsaid lm, comprising a tubular opaque frame mounted for rota-- tion ina plane transverse to the longitudinal axis of the beam, forinterrupting said beam during portions of the rotation of the frame andmovement of the iilm, and a prism of light per meable material mountedin said frame for reiracting said light beam during the timewhen saidbeam is not interrupted, toirefract said -V lengthening the timeavailable for scansioni 15. In television, the method of scanning motionpicture images projected to have a stationary period and a moving periodwhich comprises scanning throughout the stationary period, adlditionally scanning at the beginning and end of the moving period andcompensating for the Inotion of the lm during said portions of themoving period by progressive refraction.

PHILO T. FARNSWORTH. i

